A tensioner for an endless power transmission belt that provides both belt tensioning and dampening.
In the art of transmitting power employing an endless polymeric power transmission belt, such as driving or rotating driven sheaves or pulleys of a plurality of automobile accessories using a belt that is driven by a driving sheave connected to the automobile engine crankshaft, it is difficult to maintain such belt under a tension required to assure non-slipping engagement and driving of the driven sheaves. Numerous belt tensioners have been proposed and used heretofore in an effort to provide the required tension. This is especially true where one of the accessories being driven is the alternator or a combination alternator starter, the compressor of an air conditioning system, or a power steering device for the automobile because they, upon being driven, create a tight side and a slack side in the belt on opposite sides of their sheaves. The tight side has a varying tightness of a cyclic character as a function of the inherent cyclic change in the load imposed by the compressor or power steering device. Typically, a problem occurs because it is quite difficult to provide the required tension in the overall belt and prevent any tendency of the belt to move the tensioner temporally thereby creating belt slack elsewhere in the system.
It is known in the art to provide a tensioner for an endless power transmission belt where the belt is employed in driving a sheave comprising at least one accessory which upon being driven creates a slack side and a tight side in the belt on opposite sides of the sheave and the tensioner comprises a first and second support arm, each respectively having pivot means, first and second idler pulleys carried by the first and second support arms, respectively, and a pivot pin extending through the pivot means and pivotally supporting the arms adjacent opposite sides of the sheave with the first pulley engaging the slack side and the second pulley engaging the tight side to enable tensioning thereof and in a similar manner as disclosed in U.S. Pat. No. 4,416,647. This reference is hereby incorporated herein by reference.
It may be an aspect to provide an improved tensioner for an endless power transmission belt.
Another aspect may be to provide an improved tensioner that also provides dampening of the belt and thereby assures smooth running thereof free of vibration and/or oscillation.
In one manifestation there may be a tensioner for an endless power transmission belt that is driven about a sheave. The tensioner includes a base, a resilient device-that may be a spring, and first and second arms pivotally coupled for movement in an open and a closed direction. The tensioner may also comprise first and second pulleys rotatably coupled to the first and second arms, the resilient device biasing the arms in the closed direction in which the first and second pulleys apply tension to the belt. The tensioner may also comprise first and second stops positioned outside the arms on the base to limit the movement of the arms in the open direction in response to an increase in tension in the belt.
Another manifestation may be a method of assembling a tensioner for an endless power transmission belt, the belt being driven about a sheave. The method comprising the steps of providing a base, a resilient device, and first and second arms pivotally coupled for movement in an open and a closed direction. The method may also comprise the steps of providing first and second pulleys rotatably coupled to the first and second arms, the resilient device biasing the arms in the closed direction in which the first and second pulleys apply tension to the belt. The method may also comprise providing first and second stops positioned outside the arms on the base to limit the movement of the arms in the open direction in response to an increase tension in the belt.
In another embodiment during an event causing a predetermined tension on the first pulley the tensioner compensates for slack in the belt by moving the second pulley in a predetermined direction, or vice versa.
In another embodiment the tensioner may comprise bushings coupled to the arms that control travel of the arms through an interaction with the stops. The bushings may also provide a dual resistance in the tensioner with the resilient device depending on whether the arms are moving in a closed or open direction.
Another manifestation may be a method for extending a duration of use of an endless power transmission belt in an endless power transmission belt tensioning system, the belt being driven about a sheave, a tensioner in the tensioning system comprising a base, a resilient device, a pair of arms pivotally coupled for movement in an open and closed direction, a pair of pulleys rotatably coupled to the pair of arms, the resilient device biasing the arms in the closed direction in which the first and second pulleys apply tension to the belt, a pair of stops positioned outside the arms on the base to limit the movement of the arms in the open direction in response to an increase in tension in the belt. The method may comprise the steps of: detecting a predetermined condition of the belt, releasing the pair of stops from the base, moving the pair of stops so that they are coupled to the pair of arms, and fixedly coupling the pair of stops to the base.